I worked with Sound Components in Miami back in the late 70s with Peter McGrath who I think now works for Wilson.
This was the hey day of the Levinson HQD system that has been previously mentioned along with John Curl designed electronics. #6 25 watt class A amps. 2 Quads per channel stacked in a custom frame. A Decca ribbon tweeter between the two quads. The Hartleys were in huge infinite baffle enclosures. We use to listen to organ pieces and boy did those Hartleys go down low. Unfortunately, maintaining realistic levels fried a bunch of Quads and Decca ribbons. At the time the only other "subwoofer"that would go down that low was the RH (Randy Hooker) Labs Sub of which I owned two. The only electrostat that would take the abuse was the Acoustat Monitor. You put two of those on top of the RH Labs subs with Kenwood LO7 M amps driving the subs and the Dalquist DQ1 crossover and you were absolutely state of the art in the day.
There were no modern Sub drivers back then. The RH Labs used a regular 12" down firing woofer in a Helmholtz resonator which forced its response down low. Today we have modern long throw vented sub drivers that will handily out perform the Hartleys and the RH Labs in much smaller cabinets. Interestingly enough, those Kenwood amps remain amazing subwoofer amps if you can find them.
This was the hey day of the Levinson HQD system that has been previously mentioned along with John Curl designed electronics. #6 25 watt class A amps. 2 Quads per channel stacked in a custom frame. A Decca ribbon tweeter between the two quads. The Hartleys were in huge infinite baffle enclosures. We use to listen to organ pieces and boy did those Hartleys go down low. Unfortunately, maintaining realistic levels fried a bunch of Quads and Decca ribbons. At the time the only other "subwoofer"that would go down that low was the RH (Randy Hooker) Labs Sub of which I owned two. The only electrostat that would take the abuse was the Acoustat Monitor. You put two of those on top of the RH Labs subs with Kenwood LO7 M amps driving the subs and the Dalquist DQ1 crossover and you were absolutely state of the art in the day.
There were no modern Sub drivers back then. The RH Labs used a regular 12" down firing woofer in a Helmholtz resonator which forced its response down low. Today we have modern long throw vented sub drivers that will handily out perform the Hartleys and the RH Labs in much smaller cabinets. Interestingly enough, those Kenwood amps remain amazing subwoofer amps if you can find them.